The importance of automatic identification systems is ever increasing, particularly in the service sector, in the field of logistics, in the field of commerce and in the field of industrial production. Further applications of identification systems are related to the identification of persons and animals.
In particular contactless identification systems like transponder systems (for instance using an RFID tag) are suitable for a wireless transmission of data in a fast manner and without cable connections that may be disturbing. Such systems use the emission and absorption of electromagnetic waves, particularly in the high frequency domain.
Another communication scheme is the “Active Digital Aura” technology (see http://www.research.philips.com/password/archive/22/downloads/pw22_wireless.pdf, or see WO 01/15931 A1), which is based on the recognition that connecting without wires does not necessarily mean “communication over air”. The Active Digital Aura technology, for example, utilizes an electric field rather than an electromagnetic field to transmit information. By capacitively coupling the signal from a small body-worn tag into a body, an electric field is generated that extends outwardly a couple of centimeters from the entire surface of the skin. The tag, which may be built into a wristband, modulates this electric field with a unique digital identification code. Authorized devices that come close to the skin can pick up this identification code and configure themselves to a user specific personal profile, while authentication mechanisms between the tag and the device protect privacy and security. For in-home patient monitoring systems body sensors may be used that use personal identity information to automatically configure themselves to monitor specific medical conditions. This technology can furthermore be used for mobile phones or MP3 players that automatically configure themselves to personal tastes and preferences the instant a person picks them up.
WO 01/67413 discloses a radio frequency identification (RFID) system employing electrostatic technology, capacitive coupling of electric fields, electromagnetic technology, inductive coupling of magnetic fields, and combinations thereof, to communicate power and data signals to and from a source device (readers) and a remotely located transceiver (tags). In the combined electrostatic and electromagnetic communication system a single electromagnetic and electrostatic reader is provided that combines electromagnetic technology with electrostatic technology such that a reader is backward compatible and can support either electromagnetic radio frequency identification (RFID) tags or electrostatic RFID tags. A reader is designed to include both electrostatic electrodes and electromagnetic induction coils and incorporates additional modifications including those to a receiver in order for the reader to support both electromagnetic RFID transceivers and electrostatic RFID transceivers in the combination electrostatic and electromagnetic communication system.
However, the system of WO 01/67413 suffers from problems which may occur when combining such different technologies like electrostatic technology, capacitive coupling of electric fields, electromagnetic technology, and inductive coupling of magnetic fields.